This invention relates to compositions of matter useful as a catalyst system, to a method for preparing these catalyst systems and to methods for polymerization and hydrogenation utilizing the catalyst system.
The use of Ziegler-Natta type catalysts in the polymerization of olefins is well known in the prior art. In general, such systems include a Group 4 metal compound with a metal or metalloid alkyl cocatalyst, such as aluminum alkyl cocatalyst for homogenous systems or metal oxide/organo-Lewis acid activated metal-oxide for heterogeneous systems. More broadly, it may be said to include a mixture of a Group 1,2 or 13 metal alkyl and a transition metal complex from the Group 4 metals, particularly titanium, zirconium, or hafnium with homogeneous/heterogeneous cocatalysts.
Many current Ziegler-Natta processes are designed for gas phase or slurry reaction in solution, and heterogenization of homogeneous Ziegler-type catalysts to optimize polymerization activity and polymer producing properties such as stereoregularity, molecular weight, thermal/rheogical characteristics, bulky and polar comonomer incorporation and microstructure are of great advantage. Studies of homogenous Ziegler-type catalysts have shown that highly electrophilic cationic species (e.g., A) can be produced using organo-Lewis acidic (alkide/hydride abstraction) and Br.o slashed.nsted acidic (M-alkyl/H proteolysis) cocatalysts. In contrast, our overall understanding and application of analogous supported organometallic catalysts has been exclusively confined to Lewis acid surfaces or to organo-Lewis acid activated surfaces, since adsorption of metallocenes on conventional Br.o slashed.nsted acid surfaces typically results in a catalytically inert .mu.-oxo species (B) via protonolysis. ##STR1##
A design for a weakly coordinating anionic surface, derived from a very strongly Br.o slashed.nsted acidic surface is an essential key to developing new heterogeneous Ziegler-Natta processes. Recently, sulfated zirconia and related solid acids have received considerable attention because of their claimed "superacidity" i.e., stronger acidity than 100% H.sub.2 SO.sub.4 (Hammett acid value H.sub.o =-12), a property which was suggested by paraffin isomerization at room temperature. These strongly acidic sulfate group activated surfaces can be superior candidates for supports rather than MAO (methylalumoxane) or organo-Lewis acid activated ones.